During the production of optic-electronic products in the industries such as semiconductor industry, flat panel display industry and solar cell industry, it is usually required to perform a process for coating a layer of thin film on a substrate whereas the substrate can be a silicon wafer or a glass substrate for enabling the substrate to have a specific characteristic, such as electric conductivity, anti-reflection ability or the capability of a reaction film, and so on. It is noted that no matter the layer of thin film is formed by a PVD sputtering deposition device or a CVD deposition device, a high level of cleanliness or vacuum in such deposition devices is always a necessity for obtaining high-quality products whereas that can only be achieved by the use of certain vacuum systems.
The vacuum systems are referred to those required to operate under a vacuum environment, inside that the chamber thereof is vacuumed according to the characteristic of vacuum physics for dropping its interior pressure to an operation pressure so as to adapted the vacuum system for a manufacture process. Nevertheless, in addition to the vacuum environment, it still requires a feedthrough device for coupling rotary motions, linear motions, or screw motions of a mechanical device from a high-pressure (atmospheric) environment to the low-pressure (vacuum) environment of the vacuum system for powering the components inside the vacuum system to perform the manufacture process. Thus, for preventing any leakage from happening at the joint of the vacuum system and its power source, it is important to have a feedthrough device capable of achieving static seal and dynamic seal simultaneously between the vacuum system and its power source.
In a conventional rotary motion feedthrough device, there are a magnet and a ferrofluid unit being arranged between its rotation shaft and base in addition to those essential components such as bearings and seals. By the interaction between magnet and the ferrofluid with the metallic shaft and base, the shaft can be permit to turn freely but serves to block the flow of gas axially along the shaft, thereby allowing a pressure difference to exist between the “atmosphere” and “vacuum” sides, respectively, of the feedthrough device, which are exemplified in the disclosures of U.S. Pat. No. 6,857,635 and TW Pub. No. 435684.
However, such rotary motion feedthrough device using magnetic coupling not only can be very expensive, but also it can not function normally under an environment of temperature higher than 80° C. since the ferrofluids in the ferrofluid unit may lose their magnetic properties at such sufficiently high temperatures, and thereby, cause the airtight isolation between the atmosphere side and the vacuum side to fail.
In addition, there are already many studies designed for achieving the aforesaid isolation between the atmosphere side and the vacuum side without the use of the aforesaid ferrofluid magnet coupling. One of which is a vacuum rotary motion feedthrough device disclosed in TW I247855, which can achieve the airtight isolation by the arrangement of O-rings between the base and the shaft and forming the base as a stepwise structure.
Nevertheless, if the O-rings are not expanded by pressure, the airtight isolation might not be sufficient since there may be insufficient contact between the O-rings and the shaft may be too small or simply without contact therebetween, as disclosed in TW Pub. No. 435684. On the other hand, when the O-rings are not expanded by pressure and tightly pressed upon the shaft, the O-rings may be worn off by the turning of the shaft. In addition, as the operating vacuum system may produce heat that is transmitted to the shaft, the base and the O-rings, the aging of the O-rings can be enhanced by the resulting high temperature and thus cause the airtight isolation between the atmosphere side and the vacuum side to fail.
Therefore, it is in need of an improved vacuum apparatus of rotary motion entry capable of transmitting motions into a vacuum system while maintaining the vacuum of the vacuum system during the operation of the vacuum system.